Generally described, organizations operate computer networks that interconnect numerous computing systems in support of the organizations' operations. Data centers may house significant numbers of interconnected computing systems, such as private data centers operated by a single organization and public data centers operated by third parties to provide computing resources to customers. Public and private data centers may provide network access, power, hardware resources (e.g., computing and storage), and secure installation facilities for hardware owned by an organization or its customers.
To facilitate increased utilization of data center resources, virtualization technologies allow a single physical computing machine to host one or more instances of virtual machines that appear and operate as independent computer machines to a connected computer user. With virtualization, a single physical computing device can create, maintain, or delete virtual machines in a dynamic manner. In turn, users can request computer resources from a data center and be provided with varying numbers of virtual machine resources on an “as needed” or “as requested” basis. In addition to virtual machines, a data center may provide other computing resources, including hardware computing capacity, data storage space, network bandwidth, and the like.
In some environments, multiple users can share access to resources. For example, a first and a second user can have access to network-based data repositories provided by a network service provider. In such applications, the network service provider can experience concurrent commands to execute on the shared resources.